Fuse construction



May 20, 1958 EARLE 2,835,764

FUSE CONSTRUCTION Filed April 1, 1957 2 Sheets-Sheet l \NVENTOR RALPH H.EARLE ATTORNEY May 20, 1958 R. H. EARLE 2,835,764

FUSE CONSTRUCTION Filed April 1, 1957 2 Sheets-Sheet 2 o H 33 RALFH H.EARL 30 P16 3 BY Whiz :2

ATTORNEY United States Patent FUSE CONSTRUCTION Ralph H. Earle,Wauwatosa, Wis., assignor to McGraw- EdlSOIl Company, DelawareApplication April 1, 1957, Serial No. 649,770

6 Claims. 61. 200-414) 1 This invention relates to a circuit interrupterof the expulsion fuse type.

This invention is an improvement over that disclosed in the applicationof William E. Bracey, Serial No. 610,171, filed September 17, 1956, forexpulsion fuse construction and assigned to the same assignee as thepresent invention.

In the development of this type of invention an expulsion fuseconstructed was employed in which the fuse link could operate in thenormal capacity on overload to extinguish the are within the fusetube'by an expulsion action. The next step in the development of thegeneral invention was to provide in addition to the normal action of theexpulsion fuse construction, a further mode of operation whereby thefuse link could be manually broken or interrupted within the fuse tube,while carrying normal load current by manual manipulation of suitableparts of the device. Under these conditions the same type of expulsionaction took place and the device cleared itself within the fuse tube ina sure and reliable manner. However, it was found that certain types offuse links required an excessively long pull and, to meet this demand,fuse link rupturing manually operable means were added to the expulsionfuse tube construction whereby the stroke of the fuse link extractinglever was very much increased upon operation of a manually manipulableor operable lever. However, it was found that this change caused alesser pull on the fuse link throughout the entire stroke thanheretofore, because of the lengthened stroke of the fuse link extractinglever.

This invention, as stated, is an improvement over the precedinginvention last noted hereinabove. in the present construction a primaryobject of the invention is to divide the stroke of the fuse linkextracting lever and the manually manipulable lever into two portions,the first portion being obtained without sacrificing the intensity orforce of the pull exerted on the fuse link, and the second portion ofthe stroke being provided so as to have a very long stroke of the fuselink extracting lever which necessarily lessened the pull on the fuselink throughout this second portion of the stroke. The above notedarrangement produced a very desirable result indeed and could besatisfactorily used with common types of fuse links which require a verylong pull such as those which had a strain wire that took the normalstrain of the fuse link and a fusible section which had to be greatlyelongated before it ruptured. With this invention the strain wire isfirst broken as a heavy pull is placed thereon, and following this, alighter pull is placed on the fusible section, this lighter pull,however, being accompanied by a very much elongated stroke of the fuselink extracting lever.

An embodiment of the invention is shown in the accompanying drawings inwhich:

Figure l is a side elevation of the apparatus.

Figure 2 is a view of the fuse tube assembly with parts broken away andparts in section.

Figure 3 is a bottom view of the structure shown in Figure 2.

Milwaukee, Wis., a corporation of Figures 4 and 5 are views showing themanually operable lever and associated parts in successive positionsdurmg the manual rupturing of the fuse link.

Referring to the drawings it will be seen that the fuse tubeconstruction comprises a support assembly indicated generally by thereference character 1, and an expulsion fuse tube assembly indicatedgenerally by the reference character 2. The support assembly comprisesan elongated insulator 3 provided with upper and lower stationarycontacts indicated generally by the reference characters 4 and 5,respectively. The upper stationary contact 4 comprises a spring member 6provided with a shouldered portion '7 behind which projecting pins 8 ofthe upper contact 14 of the fuse tube are positioned to yieldingly lockthe upper end of the fuse tube in position, the fusetube being pivotallysupported from the hooklike members 9 of the lower stationary supportingcontact 5. The fuse tube has trunnions or pins 10 on a fuse linkextracting lever 11, and the pins or trunnions 16) are removablyreceived in the hooklike members 9.

The fuse tube 12 is a dropout expulsion type fuse tube and is closed atits upper end by means of the screw cap 13 and is open at its lower endas shown in the prior construction. As in the prior construction, theupper movable contact 14 of the fuse tube assembly-2 has a ferrulesecured to the upper end of the fuse tube 12. This ferrule is providedwith a downwardly and outwardly opening eyelet 15 adapted to receive aswitch stick so that the fuse tube may be rocked into service positionabout the pivoted lower end.

The fuse tube houses a fuse link indicated by the reference character 16and this link is provided with a disclike upper portion 17 which isclamped in position by the screw cap 13 as shown in Figure 2 anddescribed in the prior application. The fuse link leader 18 extends fromthe open lower end of the fuse tube 12 and over the outer end or lip 19of the fuse link extracting lever 11 as shown most clearly in Figure 2;

Between the upper portion of the fuse link and the lower portion thereofa strain wire 20 is positioned and an elongated fusible member 21 isloosely coiled about the strain wire and joins the upper and lowerportions of the fuse link as shown in Figure 2.

Under normal conditions when an overload occurs the strain wire 29 isruptured and the parts of the fuse link separate due to the pull of thefuse link extracting lever 11 which is actuated by the weight of thefuse tube 12 and associated parts and by the downward pressure exertedby the spring portion 6 of the upper contact. The fusible section 21immediately melts on overload after the strain wire is melted andrupture occurs between the two sections of the fuse link, the resultingare being extinguished by expulsion action within the fuse tube 12.

The lower contact of the fuse tube includes the lower ferrule or member22 secured to the lower portion of the fuse tube 12 and provided with arearwardly extending arm 23 suitably apertured to receive the hooklikeend of the switch stick so that the fuse tube may be positioned in thelower contact supporting prongs or hooklike members 9 in the usualmanner.

The fuse link extracting lever 11 is pivoted on the extension 23 of theferrule 22 of the fuse tube assembly 2. A manually manipulable member isprovided, and is indicated by the reference character 24. It has a pairof spaced segmental gears indicated at 25 and straddles the ferrule 22and is pivoted thereon as indicated at 26. It is provided with an arm 27which projects outwardly, as shown in Figure l, and which is providedwith a notch 27' to receive the hooklike portion of the switch stick sothat it may be pushed upwardly by the switch stick and to cause anupward rocking of the manually manipulable member 24 through thesuccessive positions shown in Figures 1, 2, 4 and 5. If desired, the arm27 may project in the opposite direction from that shown, so that itrequires a downward pull.

It is to be noted that the fuse link extracting lever 11 is providedwith segmental gears 28, see Figures 1, 2, 4 and 5, which mesh with thesegmental gears 25.

The manually operable member 24, which is pivoted at 26 on the ferrule22, is provided with a cam portion, indicated at 29, against which theupturned portion or lip 19 of the fuse link extracting lever ll bears. Apair of small links 39 loosely connect the fuse link extracting lever 11and the manually manipulable member 24. It is to be noted that theselinks 30 are pivoted on the fuse link extracting lever 11, as indicatedat 31, and are provided with elongated slots 32 which slidably receivere pins 33 carried by the manually operable member 2-4. These links donot transmit motion from the manually manipulable member or lever 24 tothe fuse link extracting lever 11 but merely serve to tie them togetherloosely-without having any other function than this.

The operation of the apparatus is as follows:

Under normal conditions an overload ruptures the fuse link in the usualmanner and an expulsion action takes place in the fuse tube and clearsthe line. However, when it is desired to interrupt the circuit while thedevice is carrying load current it is done manually by pushing upwardlyon the lever or extension 27 of the manually manipulable member 24 andthereby rocking it in a counterclockwise direction as viewed in Figures1, 2, 4 and 5. The first portion of the stroke results in moving thefuse link extracting lever 11 through the action of the cam 29 and thelip 19 of the fuse link extracting lever 11. At this time the greatestmechanical advantage is obtained and consequently the greatest pull isexerted on the fuse link thereby rupturing the strain wire at theinitial portion of the stroke. Continued upward motion of the arm 27 ofthe manually manipulable member 24 results in the engagement of thesegmental gears and 28. This is accompanied by a rapid or extensiverocking motion of the fuse link extracting lever 11 which causes it toquickly move from the position shown in Figure 4 through the positionshown in Figure 5 to thereby greatly and rapidly extend the fusibleportion of the fuse link. However, at this time only a light pull isrequired to rupture the fuse link but a long pull is required and isobtained by this construction. The fuse link therefore althoughrequiring a long stroke is easily ruptured within the fuse tube and anexpulsion action takes place and the line is cleared.

It will be seen that this invention provides a novel form of expulsionfuse construction in which normal action on overload is obtained and inwhich also the fuse link can be ruptured within the fuse tube bymanually manipulable means which require only a slight effort on thepart of the user. Particular attention is called to the fact that thisinvention provides the greatest mechanical advantage at the initialportion of the operation of the apparatus when it is manually operated,and results in the greatest pull on the fuse link at this portion of thestroke. As the stroke progresses, a lesser pull is exerted but a longerpull is obtained, thereby insuring rupture of the fuse link within thefuse tube even when a fuse link requiring a long pull is used.

Although this invention has been described in considerable detail it isto be understood that such description is intended as illustrativerather than limiting as the invention may be variously embodied and isto be interpreted as claimed.

I claim:

1. A drop out expulsion fuse tube construction comprising a supportassembly having upper and lower stationary contacts; a fuse tubeassembly comprising a fuse tube closed at its upper end and open at itslower end and having upper and lower movable contacts normally engagingsaid upper and lower stationary contacts, a fuse 4 link extractingmember pivoted at a fixed point on the lower portion of said fuse tubeassembly and having a rearwardly located trunnions pivotally supportedfrom said support assembly, a fuse link within said fuse tube andextending outward from the lower open end thereof and electricallyconnecting said upper and lower movable contacts, an operating armpivoted at a fixed point on said fuse tube assembly and having cam meansengaging said fuse link extracting member for moving said fuse linkextracting member through a predetermined distance upon motion of saidoperating arm, gear means initially having two disconnected gears one ofwhich is carried by said fuse link extracting member and the other ofwhich is carried by said operating arm, said two members of said gearmeans coming into mesh upon further motion of said operating arm aftersaid cam portion has finished its motion in operating said fuse linkextracting member, whereby an initially heavy pull is impartedto saidfuse link and is followed by an extended and lesser pull.

2. A drop out expulsion fuse construction comprising a support assemblyhaving upper and lower stationary contacts; a fuse tube assemblycomprising a fuse tube closed at its upper end and open at its lower endand having upper and lower movable contacts normally engaging said upperand lower stationary contacts, a fuse link within said fuse tubeelectrically connecting the upper and lower contacts of said fuse tubeand extending outwardly from the lower open end of said fuse tube, afuse link extracting member pivotally supportedfrom said fuse tubeassembly and having rearwardly located trunnions pivotally supportedfrom said support assembly, operating means including an operating armpivoted at a fixed point on said fuse tube assembly and having cam meansfor moving said fuse link extracting member with a large force for theinitial portion of the motion of said operating arm and having gearmeans including normally disengaged gears,

one of said gears being secured to said fuse link extracting" member andthe other of said gears being secured to said operating arm, said gearsbeing arranged to come into mesh upon continued motion of said operatingarm after said fuse link extracting member has been moved by said cammeans. A

3. A drop out expulsion fuse construction comprising a support assemblyhaving upper and lower stationary contacts; a fuse tube assemblycomprising a fuse tube closed at its upper end and open at its lower endand having upper and lower movable contacts normally engaging said upperand lower stationary contacts, a fuse link within said fuse tubeelectrically connecting the upper and lower movable contacts andextending outwardly from the lower open end of said fuse tube, a fuselink extracting member pivoted at a fixed point on the lower portion ofsaid fuse tube assembly and having rearwardly located trunnionspivotally supported from said support assembly, said fuse linkextracting member being controlled by said fuse link and normallyholding said fuse tube assembly in service position, an operating memberincluding an operating arm, said operating member being pivoted on saidfuse tube assembly, said operating member having cam means normallyengaging said fuse link extracting member for the initial portion of themotion of said operating arm and having a pair of gears arranged to comeinto mesh upon continued motion of said operating arm to give a furtherstroke to said fuse link extracting member after said cam means hasbecome inelfective.

4. An expulsion fuse construction comprising a supporting member, anexpulsion fuse tube carried by said supporting member and having upperand lower contacts, a fuse link electrically connecting the upper andlower contacts and located within said fuse tube, a fuse link extractingmember pivoted at a fixed point on said fuse tube, an operating memberprovided with an operating arm and pivotally supported upon the lowerportion of said fuse tube assembly, said operating member having a camportion normally engaging said fuse link extracting member for movingsaid fuse link extracting member through the initial portion of the fuselink extracting stroke and having gears carried by said fuse linkextracting member and said operating member and being normallydisengaged and coming into mesh when said cam means has becomeineffective to move said fuse link extracting member, whereby motion ofsaid operating member will cause initial motion of said fuse linkextracting member by said cam means to be supplemented by further motiondue to the interengagement of said gears.

5. A fuse construction comprising a support assembly having upper andlower stationary contacts, a fuse tube assembly comprising a fuse tubehaving upper and lower movable contacts normally engaging the upper andlower stationary contacts, a fuse link within said fuse tubeelectrically connecting the upper and lower movable contacts andextending outwardly from one end of the fuse tube, a fuse linkextracting member pivoted at a fixed point on the lower portion of saidfuse tube assembly, said fuse link extracting member being controlled bysaid fuse link and normally holding said fuse tube in service position,an operating member including an operating arm, said operating memberbeing pivoted on said fuse tube assembly and having motion transmittingmeans coacting with said fuse link extracting member for the initialportion of the a motion of said operating member, said operating memberand said fuse link extracting member having a pair of gears arranged tocome into mesh upon continued motion of said operating arm to give afurther stroke to said fuse link extracting member after said motiontransmitting means has become ineffective to rupture said fuse link.

6. A fuse construction comprising a support assembly having upper andlower stationary contacts, a fusetube assembly comprising a fuse tubehaving upper and lower movable contacts normally engaging said upper andlower stationary contacts, a fuse link within said fuse tubeelectrically connecting the upper and lower movable contacts andextending outwardly from one end of said fuse tube, a fuse linkextracting lever pivoted at a fixed point on the lower portion of saidfuse tube, said fuse link extracting lever being controlled by said fuselink, and an operating member including an operating arm, said operatingmember being pivoted on said fuse tube assembly, said operating memberhaving cam means normally engaging said fuse link extracting lever forthe initial portion of the motion of said operating arm, a pair of gearsone of which is operatively associated with said fuse link extractinglever and the other of which is operatively associated with saidoperating member, said gears being arranged to come into mesh to give afurther stroke to said fuse link extracting lever after said cam meanshas become ineffective.

References Cited in the file of this patent UNITED STATES PATENTS2,310,466 Schultz et al. Feb. 9, 1943 2,400,850 Steinmayer et al May 21,1946 2,737,551 Curtis et a1. Mar. 6, 1956

